Send Data from JavaScript to Delphi (firemonkey)

In Delphi , With below code I can send data to Javascript and it work well , but how can send data from Javascript to Delphi ?

first , I Use below code in Javascript but did not work :

JS_DELPHI._geta() ;

even below code did not work :

TMyExtension._geta() ;

I think my code in Delphi have not some essential code.

unit Unit1;

interface

uses
  System.SysUtils, System.Types, System.UITypes, System.Classes, System.Variants,
  FMX.Types, FMX.Controls, FMX.Forms, FMX.Graphics, FMX.Dialogs,
  FMX.Controls.Presentation, FMX.StdCtrls, ceffmx, FMX.Edit ,   ceflib ,
   uCEFBaseRefCounted, uCEFInterfaces, uCEFTypes, uCEFListValue, uCEFBrowser, uCEFFrame, uCEFRequest,
  uCEFv8Context, uCEFv8Exception, uCEFv8StackTrace, uCEFDomNode, uCEFProcessMessage, uCEFApplicationCore;

type
  TForm1 = class(TForm)
    ChromiumFMX1: TChromiumFMX;
    Button1: TButton;
    Edit1: TEdit;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);

  private
    { Private declarations }
  public
    { Public declarations }
  end;


   type
//这里建议用class  不建议用class(TThread)  不然有些地方要报错
TMyExtension = class(TThread) // or just class, (extension code execute in thread)
  public
  class function _geta:string;
end;

TCustomRenderProcessHandler = class(TCefRenderProcessHandlerOwn)
protected
    procedure OnWebKitInitialized; override;
end;


var
  Form1: TForm1;
  d : Integer   ;
  m : TMyExtension ;
  CefRenderProcessHandler : TCustomRenderProcessHandler ;

implementation

{$R *.fmx}
{$R *.LgXhdpiPh.fmx ANDROID}
{$R *.XLgXhdpiTb.fmx ANDROID}
{$R *.SSW3.fmx ANDROID}

procedure TForm1.Button1Click(Sender: TObject);
begin
ChromiumFMX1.Load('http://localhost/index.html');

 Edit1.Text := '555 ';

  ShowMessage('hiiiiiiiiiiiiiiiii');
end;


procedure TForm1.Button2Click(Sender: TObject);
begin
ChromiumFMX1.Browser.MainFrame.ExecuteJavaScript(' d1();',ChromiumFMX1.browser.MainFrame.GetURL, 0);
end;


class function TMyExtension._geta: string;
begin
ShowMessage('dddddddddddddddddddddddd');
  Result:='salam';
end;

procedure TCustomRenderProcessHandler.OnWebKitInitialized;

begin
    {$IFDEF DELPHI14_UP}
    TCefRTTIExtension.Register('JS_DELPHI', TMyExtension);
  {$ENDIF}
end;



initialization
  CefRemoteDebuggingPort := 9000;
  CefRenderProcessHandler := TCustomRenderProcessHandler.Create;
  CefBrowserProcessHandler := TCefBrowserProcessHandlerOwn.Create;
end.

end.